In this paper, a novel method for stiffness compensation in 
compliant mechanisms is investigated. This method involves tuning 
the ratio between the first two critical buckling loads. To 
this end, the relative length and width of flexures in two architectures, 
a stepped beam and parallel guidance, are adjusted. Using 
finite element analysis, it is shown that by maximizing this ratio, 
the actuation force for transversal deflection in post-buckling is 
reduced. These results were validated experimentally by identifying 
the optimal designs in a given space and capturing the 
force-deflection characteristics of these mechanisms.In this work, the effect of matching the first two buckling 
loads on the mechanical behavior is investigated for two compliant 
mechanisms architectures. By changing the relative length 
and width of the flexures in said architectures, the ratio between 
the first two critical loads is tuned. Maximizing this ratio for 
a certain architecture returns a minimal actuation force in postbuckling, 
which is shown through finite element analysis and experiments. 
For a parallel guidance mechanism, an increase in 
this ratio results in a decrease of absolute stiffness between the 
steep ends of the force-deflection characteristic. The ratio may 
approach unity, resulting in a nearly zero and flat actuation force. 
In a stepped beam architecture, a unity ratio is not obtainable; 
however, maximizing it reduces the distance between load paths 
in the force-deflection characteristic and therewith the energy required 
for moving between equilibrium positions. These results 
indicate that the critical buckling load ratio is a useful method 
for stiffness compensation in compliant mechanism and may be 
used to achieve static balancing.

Effect of Matching Buckling Loads on Post-Buckling Behavior in Compliant Mechanisms

Paper Proceedings: https://asmedigitalcollection.asme.org/IDETC-CIE/IDETC-CIE2021/volume/85369

ASME 2021 International Design Engineering Technical Conferences & Computers and Information in Engineering Conference (IDETC/CIE2021)

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